This specification relates to systems, apparatus and techniques for optical sensing in various applications.
Tunable light sources can be used to measure concentrations of molecules in gaseous or other media by absorption spectroscopy measurements. Examples of such tunable light sources include tunable lasers, e.g., tunable diode lasers (TDLs), and other near- and mid-infrared optical sources. Absorption spectroscopy allows measurements of gas concentration using the well-known Beer-Lambert law, which relates the amount of light absorbed due to a transition corresponding to a particular energy at a wavelength of light to the product of the concentration, the optical path length, and the wavelength-dependent absorption coefficient of the absorbing species. The specific wavelength or wavelengths probed correspond to particular energies associated with quantum-mechanical transitions in the molecule being measured.